The present invention relates to an information display device for a camera, and in particular, to a liquid crystal display that displays exposure-related information and information that is imprinted into a film.
Most cameras of present age are electronically controlled and comprising microcomputers as vital elements as well as peripheral circuits and peripheral units, wherein various functions are provided for easy exposing operation and special effects..
FIG. 4 illustrates a circuit constitution of an electronically controlled camera according to the invention. To a microcomputer 11, ON/OFF signals are fed as control commands from various operation/control switches. These operation/control switches include contact switches 12 and 13 that are synchronous with an operation of a release button, and contact switches 14 and 15 that are synchronous with an operation of a zoom switch. Moreover, button switches 17 through 22 are provided to set an exposing mode, a display mode of a liquid crystal display 16, and a superimposing mode. Based on the ON/OFF signals from these operation/control switches, the microcomputer 11 performs various types of controlling. The peripheral circuits and units include a photometric IC device 23 and a photodiode 24 both for external luminance measurement; a shutter driving motor-control IC device 25 and a motor 26 both for driving and controlling the shutter; a focus lens driving control IC device 27 and a motor 28 both for shifting the focus lens to a focal position; a strobe control circuit 29 and a discharge tube 30 both for controlling flashing and discharging of the strobe; a focusing control circuit 31, an infrared light emitting diode 32, and a semiconductor-position detector (PSD) 33, each for detecting the distance to a subject; a zoom-lens driving control circuit 34 and a motor 35 both for shifting a group of movable lenses in the zoom lens to a position for an optimum focal distance; a film feed control circuit 36 and a motor 37 both for winding up or back a film; and a power circuit comprising a battery 38 and a power switch for a peripheral circuits.
These peripheral circuits respond to commands or control signals from the microcomputer 11, and returns measurement signals and status signals to the microcomputer 11, whereby the microcomputer 11 performs programed controllings in order to accomplish the required exposing conditions. For example, once the release button is pressed, the microcomputer upon reception of an ON signal from the contact switch 12 controllingly performs photometry and range-finding, and then adjusts the position of the focus lens based on the resultant signals; and at the same time, the microcomputer verifies the shutter speed and chooses a status of the strobe. Upon reception of an ON signal generated by the actuation of a second-stage contact switch 13 on the release button, the microcomputer performs exposing by means of actuation of the shutter and controlled flashing of the strobe; and then, the film is wound up, and indications for film-winding status and film counter are updated at same time.
Prior to picture-taking, by the manipulation of a drive mode switch 21, the present exposure mode rotates from regular exposing mode to single exposure mode, continuous exposure mode, and self start mode; and it is indicated on the display. Depending on the manipulation of a function mode switch 19, one of the multiple exposure mode, bulb mode, and interval mode can be selected. After a relevant mode is selected, selection of a data change position with a select switch 18 and various data settings, such as a number of times for multiple exposure and interval time with an adjust switch 17, are performed.
Next, upon initiation of exposure control, appropriation of the power level of a battery 38 is to be checked. This checking procedure is achieved by A/D conversion of the voltage of the power switch 39, with the microcomputer 11 comparing with the reference voltage data. As described above, in a camera having battery checking means, check on the power level of the battery has been conventionally performed by comparing the power level with a specific reference voltage. Accordingly, even if the power level drops to a lowest permissible voltage, exposure control allows normal exposing. However, if the exposing mode is interval, a picture-taking operation possibly becomes impossible in the course of exposing. More specifically, in the interval mode, a predetermined number of frames is unconditionally subjected to exposing and film forwarding at predetermined intervals. And, therefore, even being at a proper level at the first frame exposing, the power of the battery may drop to an impermissible level before exposing for the final frame. This voltage drop possibly results in immobilization or expersing defects such as being underexposed, and out of focus.
One possible measure to solve this problem is to set higher the lowest permissible voltage level. However, this measure judges that a battery comes to the end of its service life while it is still useful, and causes a waste of a useful battery.
The first object of the invention is to provide a battery check device that eliminates the waste of a useful battery and allows a reliable exposing in the interval mode.
By the interval exposure control, exposing and frame forwarding are automatically performed at predetermined time intervals until a predetermined number of picture is taken. For focusing control in the interval exposure, the focal length is either fixed to the initial position, or readjusted for each frame. The fixed focusing has a problem pictures are readily out of focus when they are taken for a movable subject such as an animal. This problem can be solved by the readjusting focus control. However, with the latter focus control, if a subject is within a minimum exposure range, a warning is issued and exposure is inhibited as well as a regular exposing. Accordingly, in the interval exposing, if a subject is within the minimum exposure range, the corresponding frame is not exposed (one frame skipped); therefore, problems, such as that the cause of unexposed frame is not detected in an unattended interval exposing, occurs.
One possible measure to solve this problem is to perform exposing with focus unlocked. However, this measure poses another problem that a photographer may fail to notice that the camera is set at an out-of-focus position and performs an interval exposing. As a result, all or almost of all the frames can be exposed out of focus.
The third object of the invention is to provide an interval exposure control device that eliminates skipped frames with decreasing the possibility of out-of-focus exposure.
Exposure related information such as selections of different kinds of mode, data settings, film frame position, bulb time, and interval time are indicated on the liquid crystal display (LCD) 16. The LCD 16 also indicates data such as a date being imprinted on a film. Namely, in the vicinity of film surface at the inside of camera is provided an internal liquid crystal indication part (not shown in the drawings) for indicating an information to be exposed on the film. Indication controlling system by the microcomputer 11 is so constituted that the internal liquid crystal indication part is adapted to indicate the information identical with that of the liquid crystal display 16. FIG. 5 illustrates a display pattern on the LCD 16 that comprises display segments for single exposure mode "S", continuous exposure mode "M", multiple exposure mode "ME", bulb mode "Bulb", interval mode "INIV", and that also comprises a numerical display section N for displaying present film frame position and multiple exposure timing, and a multi-digit numerical display TN for time display of interval timer as well as for date display.
Information display on the LCD 16 is controlled by the microcomputer 11, wherein a same numerical indicator selectively displays date from the imprinting information or left time at the bulb mode; or elapsed interval time. In the case of a display pad which has a part commonly used for plural indications, the indication of informations, such as date and time, is switched based on the present status of exposure control.
As described above, in a prior art information display device, which selectively displays exposure related information and imprinting information, the display normally displays exposure related information, and switches to imprinting information to be also displayed on the internal liquid crystal indication part for exposing it on the film surface once picture-taking control starts (a contact switch 12 on the release button is turned ON). Accordingly, a photographer cannot monitor the exposure related information while picture-taking control is working. For example, in the case of picture-taking in the interval mode, the numerical display section of the LCD 16 switches to the imprinting date after picture-taking control starts, and a photographer fails to monitor the interval time elapsed.
To solve the above-mentioned problem, one possible measure is to provide a different display for each information instead of a dual-purpose display. However, this constitution inevitably increases the number of display segments to be controlled, and a larger number of display drivers; it creates a complicated and expensive display system. Another possible measure is to provide display modes being changed by a switch operation after the initiation of exposure control. However, this measure inevitably increases the number of switches required or requires more complicated operation of a photographer.
The third object of the invention is to provide an information display device that eliminates the problem in regards with switching indication of exposure related information and imprinting information.